United States Court of Appeals

for the Federal Circuit ______________________

EGENERA, INC.,

Plaintiff-Appellant

v.

CISCO SYSTEMS, INC.,

Defendant-Appellee

______________________

2019-2015, 2019-2387

______________________

Appeals from the United States District Court for the 

District of Massachusetts in No. 1:16-cv-11613-RGS, Judge 

Richard G. Stearns.

______________________

Decided: August 28, 2020

______________________

DAN L. BAGATELL, Perkins Coie LLP, Hanover, NH, argued for plaintiff-appellant. Also represented by ANDREW 

DUFRESNE, Madison, WI; MARTIN GILMORE, New York, NY;

JOHN BRUCE CAMPBELL, JAMES ELROY QUIGLEY, JOEL 

LANCE THOLLANDER, McKool Smith, PC, Austin, TX; 

CHRISTOPHER THOR BOVENKAMP, Dallas, TX. 

 E. JOSHUA ROSENKRANZ, Orrick, Herrington & Sutcliffe 

LLP, New York, NY, argued for defendant-appellee. Also 

represented by EDMUND HIRSCHFELD, DANIEL A. RUBENS; 

ELIZABETH MOULTON, Menlo Park, CA; MARK S. DAVIES,

ETHAN P. FALLON, ANNE SAVIN, Washington, DC; BRIAN 

Case: 19-2015 Document: 68 Page: 1 Filed: 08/28/2020
2 EGENERA, INC. v. CISCO SYSTEMS, INC.

LEARY, JONAS R. MCDAVIT, TAMIR PACKIN, Desmarais LLP, 

New York, NY. 

 ______________________

Before PROST, Chief Judge, REYNA and STOLL, Circuit 

Judges.

PROST, Chief Judge.

Egenera, Inc. (“Egenera”) sued Cisco Systems, Inc. 

(“Cisco”) in the United States District Court for the District 

of Massachusetts, alleging that Cisco’s enterprise server 

systems infringe various claims of U.S. Patent 

No. 7,231,430 (“the ’430 patent”). 

Prior to claim construction, and alongside an ongoing 

inter partes review (“IPR”) proceeding, Egenera separately 

petitioned the United States Patent and Trademark Office 

(“PTO”) to remove one of the eleven listed inventors from 

the ’430 patent. Following the district court’s claim construction and a trial on inventorship, Egenera asked the 

district court to add the removed inventor back to the patent. The district court determined that judicial estoppel 

prevented Egenera from relisting the inventor and held the 

’430 patent invalid for failing to name all inventors. See 

Egenera, Inc. v. Cisco Sys., Inc., 379 F. Supp. 3d 110 

(D. Mass. 2019) (“Invalidity Decision”); Egenera, Inc. 

v. Cisco Sys., Inc., 348 F. Supp. 3d 99 (D. Mass. 2019) (“Judicial Estoppel Decision”); Egenera, Inc. v. Cisco Sys., Inc., 

No. 16-11613, 2018 WL 717342 (D. Mass. Feb. 5, 2018) 

(“Claim Construction Decision”). 

Egenera appeals, challenging both the district court’s 

claim construction and the application of judicial estoppel.

For the reasons described below, we affirm the district 

court’s claim construction but vacate the invalidity judgment based on judicial estoppel and remand for further 

proceedings.

Case: 19-2015 Document: 68 Page: 2 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 3

BACKGROUND

I

Egenera owns the ’430 patent, which claims a platform 

for automatically deploying a scalable and reconfigurable 

virtual network. 

In April 2001, Egenera filed a provisional application 

that resulted in four nonprovisional applications containing the same specification. One of them resulted in the 

’430 patent, covering the “overarching system architecture.” Appellant’s Br. 12.

According to the ’430 patent’s specification, it is difficult to anticipate the amount of computing power required 

in a large organization’s physical computer network, and 

manually upgrading or deploying new physical servers is 

slow and expensive. See generally ’430 patent col. 1 

ll. 21–61. To address this, the claimed system creates a 

quickly reconfigurable virtual network environment platform. The platform “provides a large pool of processors” for 

the virtual network to use. Id. at col. 2 ll. 47–52. A subset 

may be “selected and configured” to form a “virtualized network” (or, “processing area network”) to “serve a given set 

of applications or customer.” Id. Accordingly, “processing 

resources may be deployed rapidly and easily through software” instead of through physical reconfiguration. Id. 

at col. 2 ll. 57–62. 

Claim 1, which is representative, reads:

1. A platform for automatically deploying at least 

one virtual processing area network, in response to 

software commands, said platform comprising:

a plurality of computer processors connected to an 

internal communication network;

at least one control node in communication with an 

external communication network and in communication with an external storage network having an 

Case: 19-2015 Document: 68 Page: 3 Filed: 08/28/2020
4 EGENERA, INC. v. CISCO SYSTEMS, INC.

external storage address space, wherein the at 

least one control node is connected to the internal 

communication network and thereby in communication with the plurality of computer processors, 

said at least one control node including logic to receive messages from the plurality of computer processors, wherein said received messages are 

addressed to the external communication network 

and to the external storage network and said at 

least one control node including logic to modify said 

received messages to transmit said modified messages to the external communication network and to 

the external storage network;

configuration logic for receiving and responding to 

said software commands, said software commands 

specifying (i) a number of processors for a virtual 

processing area network (ii) a virtual local area 

network topology defining interconnectivity and 

switching functionality among the specified processors of the virtual processing area network, and 

(iii) a virtual storage space for the virtual processing area network, said configuration logic including logic to select, under programmatic control, 

a corresponding set of computer processors from 

the plurality of computer processors, to program 

said corresponding set of computer processors and 

the internal communication network to establish 

the specified virtual local area network topology, 

and to program the at least one control node to define a virtual storage space for the virtual processing area network, said virtual storage space 

having a defined correspondence to a subset of the 

external storage address space of the external storage network; and

wherein the plurality of computer processors and 

the at least one control node include network 

Case: 19-2015 Document: 68 Page: 4 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 5

emulation logic to emulate Ethernet functionality 

over the internal communication network.

’430 patent claim 1 (emphasis added).

In this case, the construction of “logic to modify” is at 

issue in the context of “at least one control node . . . including logic to modify . . . received messages to transmit said 

modified messages to the external communication network.” 

Processors used by the virtual network may generate 

messages to be sent outside the network. But the outside 

network may use different protocols, see Invalidity Decision, 379 F. Supp. 3d at 125, and so there must be a way to 

modify outbound messages so that those messages will be 

compatible with the external network. This is done by the 

“logic to modify” within the “control node.” See ’430 patent

claim 1.

II

Egenera sued Cisco in August 2016 for infringement of 

the ’430 patent. In response, Cisco filed an IPR petition 

challenging all eight of the patent’s claims. 

According to Egenera, upon reviewing the ’430 patent

after Cisco’s IPR petition, it realized that all claim limitations had been conceived before one listed inventor, Mr. Peter Schulter, had started working there. Appellant’s Br.

18–19. Mr. Schulter had been hired by Egenera during the 

invention’s development for his “extensive networking experience” and to “refine and code the networking subsystem” of the invention. Id. at 11; Invalidity Decision, 379 F. 

Supp. 3d at 118. And so, one month after responding to the 

IPR petition, Egenera separately petitioned the PTO to remove Mr. Schulter as a listed inventor. Judicial Estoppel 

Decision, 348 F. Supp. 3d at 101; J.A. 9367–80. By then, 

Mr. Schulter, as well as most of the named inventors, no 

longer worked for Egenera. It is apparent that at least part 

of Egenera’s motivation to remove Mr. Schulter was to 

Case: 19-2015 Document: 68 Page: 5 Filed: 08/28/2020
6 EGENERA, INC. v. CISCO SYSTEMS, INC.

facilitate swearing behind “Grosner,” a piece of prior art 

asserted against Egenera in the IPR. See Invalidity Decision, 379 F. Supp. 3d at 114. Grosner’s priority date was 

November 2, 2000. Id. at 113. And Mr. Schulter joined 

Egenera on October 2, 2000. Id. at 112. But Egenera argued an even-earlier conception date of September 29, 

2000. Id. at 114. 

While the inventorship petition was pending, the

Board declined to institute Cisco’s IPR. J.A. 10912–28. In 

so doing, it assumed Grosner was prior art but nevertheless concluded that Cisco had not met its burden of establishing a reasonable likelihood of prevailing on the merits. 

J.A. 10922. Shortly thereafter, in January 2018, the PTO

granted Egenera’s petition and removed Mr. Schulter’s 

name. J.A. 9387.

Cisco had not argued that any of the “logic” terms 

should be interpreted as means-plus-function in the IPR,

nor in its invalidity contentions. E.g., J.A. 10368, 

12412–14. But it advanced a means-plus-function construction at the district court. And in February 2018, the 

district court issued an order construing the patent’s “logic” 

terms as means-plus-function elements. Claim Construction Decision, 2018 WL 717342, at *1, *4–10. It concluded 

that the structure in the specification corresponding to the 

claimed function of the “logic to modify” was the so-called 

tripartite structure—the combination of a virtual LAN 

proxy, a physical LAN driver, and a virtual LAN server. 

Id. at *6–7; Invalidity Decision, 379 F. Supp. 3d at 128. 

Cisco next filed an amended answer in the district 

court asserting invalidity based on pre–America Invents 

Act (“AIA”) § 102(f)—contending that Mr. Schulter invented the tripartite structure, and therefore that the patent did not list all inventors. J.A. 3238, 3251. In 

August 2018, Cisco moved for summary judgment of invalidity on this ground, which the district court denied, finding triable issues of fact regarding inventorship. Judicial 

Case: 19-2015 Document: 68 Page: 6 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 7

Estoppel Decision, 348 F. Supp. 3d at 108–09. But the court 

also rejected Egenera’s argument that if the trial showed 

Mr. Schulter to be an inventor, the patent’s inventorship 

should be corrected under 35 U.S.C. § 256(b). Id. 

at 101–02. The court reasoned that judicial estoppel precluded Egenera from “resurrect[ing]” Mr. Schulter’s inventorship. Id. at 102. 

The court conducted a three-day bench trial on inventorship. Invalidity Decision, 379 F. Supp. 3d at 112. The 

court found, in Cisco’s favor, that Mr. Schulter had conceived the tripartite structure. Id. at 125–29. The court

then reiterated that Egenera was judicially estopped from 

invoking § 256 to restore Mr. Schulter’s name, thereby 

holding the ’430 patent invalid. Id. at 129.

Egenera appealed the invalidity judgment, challenging 

the underlying construction of “logic to modify” and the application of judicial estoppel. We have jurisdiction under 

28 U.S.C. § 1295(a)(1).

DISCUSSION

I

First we address Egenera’s contention that the district 

court’s claim construction was wrong. 

At issue is the “logic to modify” limitation, which the 

district court construed as a means-plus-function element. 

For the reasons below, we agree with the district court’s 

claim construction.

The ultimate interpretation of a patent claim is a legal 

question that we review de novo. Williamson v. Citrix 

Online, LLC, 792 F.3d 1339, 1346 (Fed. Cir. 2015) (citing 

Teva Pharm. USA, Inc. v. Sandoz, Inc., 574 U.S. 318, 

331–32 (2015)). To the extent the district court makes underlying findings of fact based on extrinsic evidence, we review them for clear error. Id. 

Case: 19-2015 Document: 68 Page: 7 Filed: 08/28/2020
8 EGENERA, INC. v. CISCO SYSTEMS, INC.

Means-plus-function claiming occurs when a claim 

term invokes 35 U.S.C. § 112(f),1 which states:

An element in a claim for a combination may be expressed as a means or step for performing a specified function without the recital of structure, 

material, or acts in support thereof, and such claim 

shall be construed to cover the corresponding structure, material, or acts described in the specification 

and equivalents thereof.

We presume that claim terms with the word “means” 

invoke § 112(f) and that claim terms without the word 

“means” do not. Williamson, 792 F.3d at 1348 (en banc).2

This presumption, however, does not permit patentees to 

freely engage in functional claiming while circumventing

§ 112(f) simply by avoiding the word “means,” as we clarified in Williamson. See id. at 1349 (warning of “a proliferation of functional claiming . . . free of the strictures set 

forth in the statute”). And so the presumption against 

means-plus-function interpretation is rebuttable if a challenger demonstrates that a claim term either fails to “recite 

sufficiently definite structure” or recites “function without 

reciting sufficient structure for performing that function.” 

Id. (quoting Watts v. XL Sys., Inc., 232 F.3d 877, 880 

(Fed. Cir. 2000)). 

We clarified in Williamson that the presumption 

against means-plus-function claiming is not “strong” and 

that a challenger need not show that the limitation is “essentially . . . devoid of anything that can be construed as 

1 Although pre-AIA § 112, ¶ 6, applies in this case, 

the AIA recodified that provision as § 112(f). We use the 

AIA numbering for convenience.

2 The discussion in Williamson of the applicability of 

§ 112(f) was joined by the en banc court. 792 F.3d 

at 1347–49 & n.3.

Case: 19-2015 Document: 68 Page: 8 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 9

structure.” Id. Rather, a challenger need only show that 

the structure is not “sufficient.” See id.; TEK Glob., S.R.L. 

v. Sealant Sys. Int’l, Inc., 920 F.3d 777, 785 (Fed. Cir. 

2019). For example, “[g]eneric terms such as ‘mechanism,’ 

‘element,’ ‘device,’ and other . . . verbal constructs may be 

used in a claim in a manner that is tantamount to using 

the word ‘means’ because they ‘typically do not connote sufficiently definite structure’ and therefore may invoke

[§ 112(f)].” Williamson, 792 F.3d at 1350 (quoting Mass. 

Inst. of Tech. v. Abacus Software, 462 F.3d 1344, 1354 

(Fed. Cir. 2006)). Such terms may amount to “generic 

terms or black box recitations of structure or abstractions.” 

MTD Prods. v. Iancu, 933 F.3d 1336, 1341 (Fed. Cir. 2019) 

(quoting Zeroclick, LLC v. Apple Inc., 891 F.3d 1003, 1008 

(Fed. Cir. 2018)). Or a term may amount to a coined “nonce 

word”—that is, a word “invented . . . for one occasion only.” 

See Bryan A. Garner, Garner’s Modern English Usage 1016

(4th ed. 2016); Webster’s Third New International Dictionary (1961) (defining “nonce word” as “a word . . . coined and 

used apparently to suit one particular occasion . . . but not 

adopted into use generally”); Lighting World, Inc. v. Birchwood Lighting, Inc., 382 F.3d 1354, 1360 (Fed. Cir. 2004) 

(noting that either a “generic structural term” or a “coined 

term” can invoke § 112(f)).

If the presumption against means-plus-function interpretation is overcome, we must “identify the claimed function” and then “determine what structure, if any, disclosed 

in the specification corresponds to the claimed function.” 

Williamson, 792 F.3d at 1351. These are questions of law, 

reviewed de novo. Kemco Sales, Inc. v. Control Papers Co., 

208 F.3d 1352, 1360 (Fed. Cir. 2000).

“To determine whether the claim limitation at issue 

connotes sufficiently definite structure to a person of ordinary skill in the art, we look first to intrinsic evidence, and 

then, if necessary, to the extrinsic evidence.” TEK Glob., 

920 F.3d at 785 (citing Phillips v. AWH Corp., 415 F.3d

1303 (Fed. Cir. 2005) (en banc)).

Case: 19-2015 Document: 68 Page: 9 Filed: 08/28/2020
10 EGENERA, INC. v. CISCO SYSTEMS, INC.

A

Egenera insists that the district court erred in construing “logic to modify” as a means-plus-function limitation. 

The ’430 patent contains several “logic” terms. The district court construed them all as means-plus-function; 

Egenera challenges only the construction of “logic to modify 

said received messages to transmit said modified messages 

to the external communication network and to the external 

storage network.”

1

The district court observed that, in the claim language, 

each “logic” term was “described by a specific function” and 

was unaccompanied by “structural components.” Claim 

Construction Decision, 2018 WL 717342, at *5.

Examining the intrinsic evidence, the district court explained that “[t]he specification discloses that ‘logic’ has to 

be implemented,” id. (citing ’430 patent col. 23 ll. 23–24,

col. 25 ll. 3–4), and that such implemented logic could be 

“software logic” or “BIOS-based,” id. (citing ’430 patent

col. 3 ll. 61, 63, col. 6 l. 18). The court concluded that the 

specification was then “consistent with an understanding 

of logic as an abstraction for the set of steps designed to 

accomplish a stated function.” Id.

Egenera had argued that “logic” denotes “software, 

firmware, circuitry, or some combination thereof.” Id.

at *4. The district court noted that Egenera’s favored definition was itself “so broad and formless as to be a generic 

black box for performing the recited computer-implemented functions.” Id. at *6 (cleaned up).

Accordingly, the court concluded that the totality of the 

evidence rebutted the presumption against means-plusfunction claiming.

Case: 19-2015 Document: 68 Page: 10 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 11

2

On appeal, Egenera, pointing to its expert’s explanation and dictionary definitions, argues that “‘logic’ is a common term of art meaning software, firmware, circuitry, or

[a] combination thereof.” Appellant’s Br. 51. As Cisco argues, “logic” as used in the claims means only a “general 

category of whatever may perform” the function. Appellee’s Br. 58, 62; cf. Williamson, 792 F.3d at 1350 

(“‘[M]odule’ is simply a generic description for software or 

hardware that performs a specified function.”). 

The question is not whether a claim term recites any 

structure but whether it recites sufficient structure—a 

claim term is subject to § 112(f) if it recites “function without reciting sufficient structure for performing that function.” Williamson, 792 F.3d at 1348 (emphasis added)

(quoting Watts, 232 F.3d at 880). Egenera does not explain 

how its “logic”—even assuming it connotes some possible

structure in the general sense of software, firmware, or circuitry—amounts to “sufficient structure for performing 

[the modification] function.” See id. (emphasis added).

Egenera also argues that the “larger claim context” indicates that “logic” is structural because the “logic to modify” is part of a supposedly structural component—the 

“control node.” Appellant’s Br. 52; Reply Br. 22. But that

is not enough. Mere inclusion of a limitation within a 

structure does not automatically render the limitation itself sufficiently structural. And, again, the question is not 

whether “logic” is utterly devoid of structure but whether 

the claim term recites sufficient structure to perform the 

claimed functions. 

Egenera next argues that the claim language defines

the “inputs, outputs, connections, and operation” of the 

logic component. Appellant’s Br. 52–54 (citing Apple Inc. 

v. Motorola, Inc., 757 F.3d 1286, 1299–303 (Fed. Cir. 2014); 

Linear Tech. Corp. v. Impala Linear Corp., 379 F.3d 1311, 

1319–21 (Fed. Cir. 2004); Mass. Inst. of Tech., 462 F.3d

Case: 19-2015 Document: 68 Page: 11 Filed: 08/28/2020
12 EGENERA, INC. v. CISCO SYSTEMS, INC.

at 1355–56; and Lighting World, 382 F.3d at 1359–63); Reply Br. 23. But the cases Egenera cites do not compel its 

favored outcome and do not endorse black-box claiming. 

First, none of Egenera’s precedent considers Williamson. 

See Media Rights Techs., Inc. v. Capital One Fin. Corp., 

800 F.3d 1366, 1373 (Fed. Cir. 2015) (cautioning against 

relying on pre-Williamson precedent). Second, in those 

cases the claim language and specification provided sufficient structure to the “inputs, outputs, connections, and operation” such that the pre-Williamson strong presumption 

against means-plus-function claiming was not overcome. 

E.g., Apple, 757 F.3d at 1303 (noting that because “the 

claim language and specification outline the rules that the 

[claim term] follow[s],” the written description places clear 

structural limitations on the claim term and so the “patent 

recites a claim term with a known meaning”). In contrast, 

here the claims and specification provide no structural limitation to the “inputs, outputs, connections, and operation” 

of the claimed “logic to modify.”

We agree with Cisco: § 112(f) applies here. As used, 

“logic” is no more than a “black box recitation of structure”

that is simply a generic substitute for “means.” See Williamson, 792 F.3d at 1350. We therefore conclude that 

Cisco overcame the presumption against applying § 112(f). 

B

Egenera next argues that the district court identified 

the wrong structure as corresponding to the claimed functions of the “logic to modify” limitation. 

This limitation recites two functions: (1) “to modify said 

received messages to transmit said modified messages to 

the external communication network”; and (2) “to modify 

said received messages to transmit said modified messages . . . to the external storage network.” See ’430 patent

claim 1 (emphases added). 

Case: 19-2015 Document: 68 Page: 12 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 13

The district court concluded that the structure corresponding to the first function was “virtual LAN server 335, 

virtual LAN proxy 340, and physical LAN driver 345” and 

equivalents. Claim Construction Decision, 2018 WL 

717342, at *7. The parties call this the “tripartite structure.”

Egenera now agues on appeal that the tripartite structure is too broad. Appellant’s Br. 55–59. Within the tripartite structure, insists Egenera, only the virtual LAN 

proxy “modifies outgoing messages.” Id. at 59. Cisco disagrees, pointing to its expert’s testimony that the proxy does 

not “act in isolation” and “cannot perform the recited function . . . by itself.” Appellee’s Br. 72 (citing J.A. 1431). Rather, the LAN proxy is merely “the middleman.” Id. at 73. 

And, argues Cisco, Egenera cannot switch the scope of its 

claim construction on appeal.

Egenera previously identified “control node 120” and 

equivalents as the corresponding structure when it argued 

at the district court. Claim Construction Decision, 

2018 WL 717342, at *7. As Cisco highlights, this control 

node is a broad structure that itself encompasses the tripartite structure. See Appellee’s Br. 70. Indeed, Egenera 

argued below that the tripartite structure was 

“overly[ ]narrow.” J.A. 3060.

Now Egenera contends that the structure it objected to 

as overly narrow must be narrowed further. Egenera explains that, below, its proposed structure corresponded to 

both claimed functions—i.e., not only messages to the “external communication network” but also messages to the 

“external storage network.” Reply Br. at 24–26. We find 

unpersuasive this explanation for Egenera’s switch in 

scope, as Egenera fails to explain how subtracting the “external storage network” portions from the “control node”

leaves us with the ultra-narrow structure it advances 

newly on appeal. 

Case: 19-2015 Document: 68 Page: 13 Filed: 08/28/2020
14 EGENERA, INC. v. CISCO SYSTEMS, INC.

We agree with Cisco that Egenera cannot now seek a 

much narrower construction on appeal. Digital-Vending 

Servs. Int’l, LLC v. Univ. of Phoenix, Inc., 672 F.3d 1270, 

1273 (Fed. Cir. 2012) (“[A] party may not, as a general rule, 

change the scope of its claim construction on appeal.”). At 

any rate, we also find the district court’s and Cisco’s reasoning persuasive on the merits. The components of the 

tripartite structure—the virtual LAN server, virtual LAN 

proxy, and physical LAN driver—function in concert to 

modify messages to transmit to the external communications network. See Claim Construction Decision, 2018 WL 

717342, at *7; ’430 patent col. 18 ll. 53–58, fig. 3B; Appellee’s Br. 72–74. 

Accordingly, we affirm the claim construction order.

II

Next we turn to Egenera’s contention that the district 

court erred in applying judicial estoppel, thereby preventing correction of inventorship and invalidating its patent

as a consequence.

A

First, we address whether Egenera could correct inventorship, even absent judicial estoppel.

The Constitution authorizes awarding patent exclusivity only to an inventor. U.S. CONST. art. I, § 8, cl. 8. And 

so courts have historically held that if a patent does not 

reflect its true inventorship, it is invalid. See Pannu v. 

Iolab Corp., 155 F.3d 1344, 1349–50 (Fed. Cir. 1998) (collecting cases). 

Inventorship is sometimes easy to determine. But 

sometimes it is complicated, as with complex projects involving many contributors at various times. Ultimately, 

inventorship is a legal conclusion premised on underlying 

factual findings, and one that depends on claim construction. In re VerHoef, 888 F.3d 1362, 1365 (Fed. Cir. 2018); 

Case: 19-2015 Document: 68 Page: 14 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 15

Trovan, Ltd. v. Sokymat SA, 299 F.3d 1292, 1302 (Fed. Cir. 

2002). And like validity, inventorship is a claim-by-claim 

question. Trovan, 299 F.3d at 1302. Accordingly, who 

should be listed on the face of a patent may vary depending 

on what, exactly, is claimed and what, exactly, a court determines the claim scope to be.

The Patent Act allows a listing of inventors to be corrected either upon petition to the Director, see 35 U.S.C.

§ 256(a), or upon court order, see § 256(b). Our precedent 

recognizes that a patent cannot be invalidated if inventorship can be corrected instead. Pannu, 155 F.3d at 1350. 

The statutory text recognizes this too:

The error of omitting inventors or naming persons 

who are not inventors shall not invalidate the patent in which such error occurred if it can be corrected as provided in this section. 

35 U.S.C. § 256(b) (emphases added). Section 256 applies 

if “through error a person is named . . . as the inventor, or 

through error an inventor is not named.” § 256(a). 

As previously noted, the inventorship question involved Egenera’s attempt to add back an inventor, 

Mr. Schulter, who had previously been removed alongside

the IPR. The district court declared in a footnote that 

Mr. Schulter’s removal by petition was therefore “a considered act that is unlikely to qualify as an omission ‘through 

error.’” Judicial Estoppel Decision, 348 F. Supp. 3d 

at 102 n.1. Cisco agrees, arguing that Egenera’s petition 

was a “tactical ploy” rather than a “reasonable, but mistaken, effort to get inventorship right.” Appellee’s

Br. 27–30 (arguing that “error” requires a “good-faith mistake”). We note that although the district court declined to 

credit Egenera’s witnesses’ accounts of conception, it also

declined to find inequitable conduct on these facts, despite 

being urged by Cisco to do so. See Judicial Estoppel Decision, 348 F. Supp. 3d at 101; Invalidity Decision, 379 F. 

Supp. 3d at 129. 

Case: 19-2015 Document: 68 Page: 15 Filed: 08/28/2020
16 EGENERA, INC. v. CISCO SYSTEMS, INC.

Our precedent provides that “error” in § 256 includes 

“all varieties of mistakes—honest and dishonest”—rather 

than only unintentional inaccuracy. Stark v. Advanced 

Magnetics, Inc., 119 F.3d 1551, 1554–56 (Fed. Cir. 1997).3 

That is, Stark expressly construed “error” to “embrace 

more than simply honest mistakes.” Id. at 1554. Stark’s 

broad interpretation was intended to “harmonize[] well 

with the title 35 policy of seeking to reward the actual inventors of technological advances.” Id. Indeed, § 256 is a 

savings provision, functioning to prevent invalidation 

when correction is available. It is the inequitable-conduct 

rules that provide a safety valve in the event of deceit. Id. 

at 1555–56. 

Cisco invites us to sidestep Stark because the AIA has 

since amended § 256. Previously, § 256 contained an additional requirement that the “error” of omitting an inventor 

occurred without “deceptive intention” on the inventor’s 

part. The scope of “error,” standing alone, was therefore 

3 Reissue under 35 U.S.C. § 251 also requires “error,” 

and our case law there is consistent with our case law on 

§ 256. See, e.g., Fleming v. Escort Inc., 774 F.3d 1371, 1380 

(Fed. Cir. 2014) (“Errors are not limited to slips of the pen 

but encompass—and most often are—deliberate drafting 

choices. Not all choices qualify . . . .” (citation omitted)); id.

(stating that error includes “deficient understandings” and 

choices that rest on “cognizable false or deficient understanding of fact or law” but not simply a “now-regretted 

choice”); In re Dinsmore, 757 F.3d 1343, 1347–48 (Fed. Cir. 

2014); In re Rosuvastatin Calcium Pat. Litig., 703 F.3d 511, 

522–24 (Fed. Cir. 2012) (applying pre-AIA language and 

including deliberate actions) (collecting cases); In re Amos, 

953 F.2d 613, 616 (Fed. Cir. 1991) (noting that error includes attorney’s mistake in understanding claim scope, 

“one of the most common sources of defects” (quoting In re 

Wilder, 736 F.2d 1516, 1519 (Fed. Cir. 1984)).

Case: 19-2015 Document: 68 Page: 16 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 17

broad enough to otherwise include acts amounting to “deceptive intention”—that is, intentional inaccuracy. See

Stark, 119 F.3d at 1554. With the AIA, “without . . . deceptive intention” was struck from that section. See AIA, Pub. 

L. No. 112-29, § 20(f)(1)(B), 125 Stat. 284, 334 (2011). The 

essence of Cisco’s position is that when Congress removed

this restrictive language that excluded intentional inaccuracy in certain cases, it somehow narrowed the meaning of 

“error” to exclude intentional inaccuracy entirely. Appellee’s Br. 30. Cisco argues that Congress’s removal of this 

language was meant to harmonize “error” with what Cisco 

views as its plain meaning—one that excludes intentional 

inaccuracy. We had not yet addressed the impact of the 

AIA on the holding of Stark. See, e.g., CODA Dev. S.R.O. 

v. Goodyear Tire & Rubber Co., 916 F.3d 1350, 1358 n.6 

(Fed. Cir. 2019). But we now reject Cisco’s proposed interpretation because it is contrary to the text of § 256, the 

structure of the AIA,4 and the AIA’s legislative history.5 

We hold that the AIA did not narrow the meaning of 

4 For instance, through the AIA, deceptive-intention 

language was removed from the reissue provision, 

35 U.S.C. § 251, as well as the analogue of § 256 that applies to patent applications, 35 U.S.C. § 116. See AIA 

§ 20(a)(3)(B), (f)(1)(B), 125 Stat. at 333–34. The § 102(f) 

improper-inventorship invalidity provision was also removed. AIA § 3(b)(1), 125 Stat. at 285–86. And newly established derivation proceedings provide for correction of 

named inventors. AIA § 3(i), 125 Stat. at 289–90 (codified 

at 35 U.S.C. § 135(b)).

5 See, e.g., 157 Cong. Rec. S1378 (daily ed. Mar. 8, 

2011) (statement of Sen. Kyl) (“Eliminating the various deceptive-intent requirements moves the U.S. patent system 

away from the 19th century model that focused on the patent owner’s subjective intent, and towards a more objective-evidence-based system that will be much cheaper to 

litigate and more efficient to administer.”). 

Case: 19-2015 Document: 68 Page: 17 Filed: 08/28/2020
18 EGENERA, INC. v. CISCO SYSTEMS, INC.

“error.” Accordingly, § 256 does not exclude “considered 

acts,” or even “deceptive intention,” from the meaning of 

“error.” Cf. Judicial Estoppel Decision, 348 F. Supp. 3d at

102 n.1. “Error” is simply the incorrect listing of inventors. 

Egenera asserted in its inventorship petition to the 

PTO, concurrent with the IPR, that Mr. Schulter was incorrectly listed as an inventor. At the time, no one had argued that “logic to modify” was a means-plus-function 

term. Indeed, it presumptively was not. And Egenera opposed such a construction when Cisco later advanced it; 

likewise, its position that Mr. Schulter was not an inventor 

was seemingly consistent with its preferred construction. 

But the court rejected Egenera’s construction in a way that 

also illuminated Mr. Schulter’s necessary presence as an 

inventor. After a three-day trial, and this appeal, the 

claim-construction and inventorship questions have at last 

been resolved. Because of these legal determinations, in 

retrospect, Egenera’s assertion in its inventorship petition

was incorrect: Mr. Schulter was an inventor. According, 

we conclude that Mr. Schulter’s omission was “error.”

B

Next we turn to judicial estoppel.6 As noted, the district court here concluded that Egenera was judicially estopped from adding Mr. Schulter’s name back to the patent 

after it held a trial establishing him to be an inventor—

thereby invalidating the patent for improper inventorship.

6 Cisco contends that Egenera waived any argument 

against judicial estoppel. Appellee’s Br. 31. Regardless, 

whether to apply the waiver rule is discretionary. Here, 

there has been complete briefing and argument on the judicial estoppel issue. See Automated Merch. Sys., Inc. 

v. Lee, 782 F.3d 1376, 1379–80 (Fed. Cir. 2015). To apply 

waiver would not serve judicial economy or promote fairness, and so we address the merits.

Case: 19-2015 Document: 68 Page: 18 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 19

As an initial matter, Egenera insists that judicial estoppel can never prevent § 256 from saving a patent’s validity. Appellant’s Br. 33–36; see Oral Arg. at 00:40–58,

No. 19-2015, http://oralarguments.cafc.uscourts.gov/default.aspx?fl=19-2015.mp3. We need not decide that issue, 

however, because in this case the criteria for judicial estoppel were not met.

For questions of judicial estoppel, we apply the law of

the regional circuit—here the First Circuit. Akamai 

Techs., Inc. v. Limelight Networks, Inc., 805 F.3d 1368, 

1374 (Fed. Cir. 2015). The legal effect of representations 

to the PTO and statutory interpretation of the Patent Act, 

however, are issues of Federal Circuit law. See Endo 

Pharm. Inc. v. Teva Pharm. USA, Inc., 919 F.3d 1347, 1352 

(Fed. Cir. 2019). Under First Circuit law, we review a district court’s application of judicial estoppel for abuse of discretion. Akamai, 805 F.3d at 1374 (citing Knowlton 

v. Shaw, 704 F.3d 1, 9–10 (1st Cir. 2013)). We accept underlying findings of fact unless they are clearly erroneous 

and review the resolution of legal questions de novo. Id. 

The First Circuit “treat[s] a material mistake of law as a 

per se abuse of discretion.” Perry v. Blum, 629 F.3d 1, 8 

(1st Cir. 2010).

Judicial estoppel is an equitable doctrine that prevents 

a litigant from taking a litigation position inconsistent with

one successfully asserted in an earlier court proceeding. 

See id. “The purpose of the doctrine is to protect the integrity of the judicial process.” Id. Although the “contours of 

judicial estoppel are hazy,” and its application is case-dependent, the First Circuit applies the New Hampshire factors. RFF Family P’ship v. Ross, 814 F.3d 520, 527–28 

(1st Cir. 2016) (Souter, J., sitting by designation). Accordingly, a court examines (1) whether a party’s earlier and 

later positions are “clearly inconsistent”—that is, “mutually exclusive”; (2) whether the party “succeeded in persuading a court to accept” the earlier position; and 

(3) whether the party would “derive an unfair advantage or 

Case: 19-2015 Document: 68 Page: 19 Filed: 08/28/2020
20 EGENERA, INC. v. CISCO SYSTEMS, INC.

impose an unfair detriment” on the other side if not estopped. New Hampshire v. Maine, 532 U.S. 742, 750–51 

(2001). 

We address the New Hampshire factors in turn.

1

First, Egenera advanced no “clearly inconsistent” positions.

To be “clearly inconsistent,” positions must be “mutually exclusive” and “directly inconsistent.” RFF, 814 F.3d

at 528 (quoting Alt. Sys. Concepts, Inc. v. Synopsys, Inc., 

374 F.3d 23, 33 (1st Cir. 2004)). 

In its § 256(a) petition, Egenera asked the PTO as a 

matter of formality “to delete Peter Schulter as an inventor 

of the invention being claimed.” J.A. 9367; see also 

37 C.F.R. § 1.324; MPEP § 1481.02 (9th ed. Rev 10.2019, 

June 2020). Cisco argues that the “clearly inconsistent positions” were the two contrary uses of § 256.7 See Oral Arg. 

at 19:05–25, 26:29–38. Here, of course, in light of the district court’s claim construction and accompanying inventorship determination, Egenera is asking the district court 

to add Mr. Schulter back as an inventor. The district court 

concluded that “Egenera’s suggestion that Schulter may be 

relisted as an inventor as circumstances may dictate” was 

clearly inconsistent with its “September 2017 petition . . . 

that Schulter’s name was erroneously listed.” Judicial Estoppel Decision, 348 F. Supp. 3d at 102. This was incorrect. 

7 If Cisco’s argument were accepted, it is hard to see 

how any inventorship correction could occur under § 256. 

By definition, a request to change inventorship would be 

inconsistent with the “position” taken at the outset of prosecution, in which inventor names are submitted with the 

application. And serial petitions would be impossible.

Case: 19-2015 Document: 68 Page: 20 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 21

We do not think that multiple corrections under § 256 

are per se “mutually exclusive.” In any event, the district 

court’s intervening claim-construction and inventorship 

determinations further justify any seeming inconsistency. 

Cf. Biomedical Pat. Mgmt. Corp. v. Cal. Dep’t of Health 

Servs., 505 F.3d 1328, 1341–42 (Fed. Cir. 2007) (noting that 

“inconsistency” in the judicial estoppel context “is excused 

by an intervening change in the law”); see generally 

18B Wright & Miller, Federal Practice & Procedure

§ 4477.3 (2d ed., Apr. 2020 update).

Inventorship, a complex legal conclusion, can depend 

on claim construction. Here, the underlying presumption 

was that Egenera’s claim terms, lacking “means,” were not 

means-plus-function. Egenera’s inventorship petition was 

consistent with that presumption. Indeed, it may well be 

that Mr. Schulter would not be an inventor under Egenera’s preferred construction; but inventorship under that 

claim construction was not decided. And Egenera consistently protested the means-plus-function construction both 

at the district court and on appeal—a construction that the 

inventorship question was directly predicated on. Therefore, once those issues were decided, it was entirely consistent for Egenera to request an accompanying formal 

correction of inventorship. Accordingly, at least due to the 

intervening claim construction, it was not “mutually exclusive,” as judicial estoppel requires, to again request formal 

correction of inventorship. 

The district court thus erred in discerning “clearly inconsistent” positions.

2

Second, Egenera did not succeed in persuading a court 

or court-like tribunal to accept its first position. 

“‘Acceptance’ in this context is a term of art.” Perry, 

629 F.3d at 11. That is, “a party need not show that the 

earlier representation led to a favorable ruling on the 

Case: 19-2015 Document: 68 Page: 21 Filed: 08/28/2020
22 EGENERA, INC. v. CISCO SYSTEMS, INC.

merits . . . but must show that the court adopted and relied 

on the represented position either in a preliminary matter 

or as part of a final disposition.” Id. And “[t]he showing of 

judicial acceptance must be a strong one.” Id. In this factor, we ask whether the earlier tribunal’s acceptance implicated the “truth-seeking function of the court.” Id. at 11 

(quoting Teledyne Indus., Inc. v. NLRB, 911 F.2d 1214, 

1218 (6th Cir. 1990)). This requirement aligns with the 

doctrine’s purpose of “safeguard[ing] the integrity of the 

courts by preventing parties from improperly manipulating 

the machinery of the judicial system.” New Hampshire, 

532 U.S. at 750.

The district court concluded that “[t]he PTO accepted 

these representations”—referring to the inventorship petition. Judicial Estoppel Decision, 348 F. Supp. 3d at 102. 

As an initial matter, the inventorship petition contained no 

underlying statements of fact—simply statements that 

Mr. Schulter’s listing was erroneous and that all the colisted inventors agreed or did not disagree. See J.A.

9367–80. The PTO did not cast these statements into the 

crucible of examination. Rather, it agreed that all the signatures and fees were in order. See J.A. 9388; MPEP 

§ 1481.02.

Egenera contends that its statements in its petition 

“did not involve the judicial process necessary for judicial 

estoppel.” Appellant’s Br. 42. Instead, the § 256 petition 

process is “ministerial” and “does not involve any tribunal, 

judicial officer, or substantive analysis.” Id. Cisco replies 

that Egenera undisputedly “persuaded” the PTO that 

“Schulter was not an inventor.” Appellee’s Br. 44. 

Under 37 C.F.R. § 1.324(b), the PTO examines a request only for the presence of supporting statements and 

the required fee. See also MPEP § 1481.02; J.A. 9388. No 

substantive examination occurs, and the PTO does not consider the substantive adequacy of the petition. Cisco argues that the First Circuit has rejected a “ministerial” 

Case: 19-2015 Document: 68 Page: 22 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 23

exception. But in explanation, Cisco points out that unexamined identification of assets during bankruptcy proceedings can ground judicial estoppel in a later bankruptcy 

proceeding. See Appellee’s Br. 45 (citing Guay v. Burack, 

677 F.3d 10, 17 (1st Cir. 2012)). We find Cisco’s arguments 

unpersuasive: bankruptcy schedules occur in the context of 

a bankruptcy court—they are specific representations of 

fact before a tribunal.8 And as Egenera argues, Cisco’s 

chosen administrative judicial-estoppel precedents involve 

“inconsistent statements about an objective fact, such as 

the existence of bankruptcy assets or a claimed disability” 

rather than “context-related legal conclusions.” Reply Br.

19.9

Accordingly, even though we agree that judicial estoppel can occur in an administrative tribunal,10 we disagree 

that a § 256 petition, without more, counts as “persuasion” 

of a “court” for judicial-estoppel purposes. 

8 Cisco also points to out-of-circuit applications of judicial estoppel related to the Social Security Administration’s acceptance of statements in a disability-insurance 

application. See Appellee’s Br. 46 n.3. Again, those cases 

are not only not binding but also unpersuasive, as they involve inconsistent statements about objective facts.

9 “[J]udicial estoppel arises only from a position 

taken in an adjudicatory proceeding. Inconsistent positions 

taken in other contexts must be measured by other theories.” Federal Practice & Procedure § 4477; see also id. 

§ 4477.2 (“A position asserted before a government official 

in nonadjudicatory proceedings . . . should not support ‘judicial’ estoppel.”). 

10 See Trs. v. United States, 593 F.3d 1346, 1354 (Fed. 

Cir. 2010) (“Judicial estoppel applies just as much when 

one of the tribunals is an administrative agency as it does 

when both tribunals are courts.” (emphasis added)).

Case: 19-2015 Document: 68 Page: 23 Filed: 08/28/2020
24 EGENERA, INC. v. CISCO SYSTEMS, INC.

This determination is narrow. We do not hold that judicial estoppel cannot apply to statements made during 

substantive prosecution, ex parte reexamination, or other 

quasi-adjudicatory proceedings—an issue not before us. 

And we do not go so far as to say that other theories of estoppel cannot apply to ministerial filings or representations before the PTO. But judicial estoppel cannot be 

stretched beyond persuading a tribunal, and it does not apply here.

3

Third, Egenera would gain no unfair advantage, and 

Cisco would suffer no unfair prejudice, if judicial estoppel 

were not applied. 

The focus of this inquiry is on whether not applying estoppel would result in unfair advantage or prejudice. See 

New Hampshire, 532 U.S. at 751 (“[Courts ask] whether 

the party seeking to assert an inconsistent position would 

derive an unfair advantage . . . if not estopped.”); RFF, 

814 F.3d at 528. 

Egenera argues that it would obtain no unfair advantage by correcting inventorship in conformance with 

the district court’s inventorship determination. Appellant’s Br. 45–46. The petition was not granted until after 

the Board denied institution of the IPR on the merits. 

Egenera points out that the petition did not affect the IPR, 

and correction would simply “foster resolution of this case 

on the merits.” Appellant’s Br. 45–46. Cisco responds that, 

as the district court noted, Egenera’s disavowal of 

Mr. Schulter’s inventorship enabled it to argue for an earlier priority date to bolster its IPR and litigation position. 

Appellee’s Br. 47; Judicial Estoppel Decision, 348 F. 

Supp. 3d at 101–02. But in any event, it ended up not making a difference. The Board considered Cisco’s prior art 

without addressing Egenera’s priority arguments. And

Cisco fails to explain how, even if there would be an 

Case: 19-2015 Document: 68 Page: 24 Filed: 08/28/2020
EGENERA, INC. v. CISCO SYSTEMS, INC. 25

advantage conferred on Egenera by failure to estop, that 

advantage would be “unfair” under these facts.

Things might be different had Egenera succeeded in 

swearing behind the prior art. We do not go so far as to 

declare that there would be no potential for judicial estoppel had the Board fully considered and adopted Egenera’s 

swearing-behind arguments. But that would be estoppel 

on the basis of a prior representation to a tribunal (i.e., the 

Board). And both prejudice and inconsistency would be 

clear: there would be the potential of two judicial decisions 

predicated on opposite inventorship statuses. But that is 

not this case. Here, there would be no unfair prejudice in 

refusing to estop. The district court did not identify any. 

See Judicial Estoppel Decision, 348 F. Supp. 3d at 101–02. 

Cisco identified none in its brief, nor when pressed at oral 

argument. See Oral Arg. at 15:30–17:34.

Cisco dismisses this prong of the New Hampshire factors as purely optional under First Circuit law, arguing 

only that it is “enough that Egenera took ‘contradictory’ positions ‘in search of legal advantage.’” Appellee’s Br. 47, 

49–50 (citing Alt. Sys. Concepts, 374 F.3d at 33). We disagree with Cisco’s reading of Alternative System Concepts, 

which would collapse the first and third prongs into one. 

And we decline to ignore abundant First Circuit precedent 

signifying the importance of this factor. E.g., RFF, 

814 F.3d at 528; Perry, 629 F.3d at 8–9. 

Accordingly, there would be no unfair advantage or unfair prejudice in refusing to estop Egenera.

4

The district court legally erred as to each New Hampshire factor. We therefore hold that the district court 

abused its discretion by applying judicial estoppel.

Case: 19-2015 Document: 68 Page: 25 Filed: 08/28/2020
26 EGENERA, INC. v. CISCO SYSTEMS, INC.

CONCLUSION

We have considered the parties’ remaining arguments 

but find them unpersuasive. For the foregoing reasons, we 

affirm the district court’s claim construction but vacate the 

district court’s invalidity judgment and the accompanying 

cost award. We remand for further proceedings.

AFFIRMED-IN-PART, VACATED-IN-PART, AND 

REMANDED

COSTS

The parties shall bear their own costs.

Case: 19-2015 Document: 68 Page: 26 Filed: 08/28/2020